LIGA is a fabrication technology used to create a plastic microstructure using high energy x-rays generated by a synchrotron. LIGA was developed in the early 1980s at Germany. Many studies have been made for advancing LIGA and applications thereof. LIGA is a German acronym for Lithographie, Galvanoformung, and Abformung. That is, LIGA includes a Lithographie process for fabricating a plastic microstructure through X-ray exposure, a Galvanoformung process for forming a mold insert using electro forming, and an Abformung process for forming a microstructure using the mold insert. LIGA was developed for mass production with high productivity, not designed for one time production of a microstructure.
A micro-electro-mechanical system (MEMS) technology uses an ultraviolet rays (UV) exposure scheme to fabricate a microstructure. Unlike the conventional MEMS technology, LIGA uses high energy X-rays to fabricate a microstructure. Due to the high energy X-rays, a microstructure having a high aspect ratio can be fabricated using LIGA. Furthermore, a microstructure fabricated by LIGA has excellent surface quality. LIGA has been used to produce micro components for optical communication, such as an optical waveguide and an optical connector, precise mechanical parts such as micro motor, and a core part for a heat exchanger and a micro reactor.
In early development stage, a Deep X-ray Lithography (DXRL) process using high energy x-rays was mainly used. Henceforth, a UV-LIGA process using a UV exposure scheme was introduced and used more as a micro-electro-mechanical system (MEMS) technology has been advanced.
In LIGA, a microstructure having the same shape of a final product is formed at first through an exposure process. Using the formed microstructure as a mother structure, a mold or a mold insert is formed by performing an electro forming process.
The final product having the same shape of the initially produced microstructure can be mass-produced through a molding process using the mold.
In order to mass-produce various microstructures through LIGA, It is necessary to precisely produce a mold or a mold insert. Furthermore, the mold must have a high dimensional accuracy and required mechanical properties as well as a shape of final product. Such requirements must be satisfied in order to stably mass-produce final products.
Recently, various microstructure fabricating technologies have been used to produce molds or mold inserts for mass-productions of various microstructures. A mold may be produced using a precision machining process or a laser process that directly processes mold material to form a mold. However, the precision machining process or the laser process has drawbacks such as low dimensional accuracy and long production time. Due to such drawbacks, an exposure process in a semiconductor process has been generally used. A microstructure is produced through an exposure process, and a metal mold or a metal mold insert is then produced by performing an electro forming process on the fabricated microstructure.
As the MEMS technology has been advanced, various exposure processes have been introduced. Such exposure process has merits of process automation, high dimensional accuracy, and high yield. A microstructure fabricated through typical exposure process has a planar shape. It is because a direction of radiating light is vertical to a substrate and photosensitive material coated on the substrate. Accordingly, it is difficult to produce a microstructure having various 3-D shapes of different heights of inclined planes in case of the vertical exposure scheme.
A microstructure having a constant slope can be manufactured through a method for radiating light using an inclined exposure scheme. However, only limited microstructures can be produced using the inclined exposure scheme. Further, it is very difficult to manufacture a mask used for the inclined exposure scheme, and complicated equipment is additionally required to use the inclined exposure scheme. Accordingly, the inclined exposure scheme has been used only for specific cases.
Moreover, the inclined exposure scheme also has limitation in depth exposed by X-rays. Accordingly, it is impossible to produce a microstructure having a complicated shaped in a width direction thereof using the inclined exposure scheme.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.